A condition produced by relatively great activity or stimulation of the sympathetic nervous system and characterized by blanching of the skin, goose bumps or goose flesh, vascular spasm, increased pilomotor activity (movement of hairs), and abnormally high blood pressure.

The oculocardiac reflex (slowing of the rhythm of the heart following compression of the eyes) is reduced or inverted, the pupils of the eyes are dilated, there is a fine rapid tremor of the hands, and insomnia often occurs.

Gastrointestinal symptoms; such as, anorexia and constipation may also be present.